Low thermal conductivity and improved figure of merit in fine-grained binary PbTe thermoelectric alloys

Fine-grained binary PbTe thermoelectric materials have been fabricated by a combination of a reflux chemical synthesis and hot pressing. The grain sizes of the hot pressed bulk samples varied from 200 to 400 nm, which significantly contributed to the thermal conductivity reduction due to the enhanced phonon scattering at grain boundaries. Low room temperature thermal conductivity of 0.75 Wm(-1) K-1 has been obtained after porosity correction for the sample with a grain size of similar to 200 nm. The highest figure of merit ZT of the fine-grained binary PbTe bulk sample reaches 0.8 at 580 K although the composition was unoptimized. The value is comparable to that of the best PbTe alloys.